DTC 43

DTC 43 - Knock Sensor Circuit:

Knock Sensor Wiring Circuit:

Circuit Description:

The knock sensor is used to detect engine detonation and allow the ECM to retard Ignition Control (IC) timing based on the signal being received. The circuitry within the knock sensor causes the ECM supplied 5 volt signal to be pulled down, so that under a no knock condition CKT 496 should measure about 2.5 volts. The knock sensor produces an AC signal which rides on the 2.5 volts DC voltage. The amplitude and signal frequency are dependent upon the knock level.

If CKT 496 becomes open or shorted to ground, the voltage will either go above 3.5 volts or below 1.5 volts. If either of these conditions are met for 20 seconds, DTC 43 will be stored.

DTC 43 will set if:
^ Ignition "ON."
^ Voltage on CKT 496 above 3.4 volts or below 1.5 volts.
^ Condition present for 20 seconds.

Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.

1. If DTC 43 is detected, "Knock Retard" on the Tech 1 will display 10 degrees.
If an audible knock is heard from the engine, repair the internal engine problem. Normally, no knock should be detected at idle.
2. The ECM applies 5 volts to CKT 496, which should be present at the knock sensor terminal.
3. This test determines if the knock sensor is faulty or if the knock sensor portion of the PROM is faulty.

Diagnostic Aids:

Check CKT 496 for a intermittent open or short to ground. Also check for proper installation of PROM.
If the KS CKT 496 is routed too close to secondary ignition wires, it may induce a voltage and cause a false knock signal.

- Intermittent Malfunctions